Apparatus for expanding perlite and the like



Oct 23, l951 E. o. HowLE ETAL APPARATUS FOR EXPANDING PERLITE AND THELIKE Filed Sept. 17. 1947 3 Sheets-Sheet, l

22 er JEC/429022 34.9702721477 ./sir c3 Oct. 23, 1.951 E, Q HOWLE ErAL2,572,484

APPARATUS FOR EXPANDING PERLITE AND THE LIKE Filed Sept. 17. 1947 3Sheets-Sheet 2 Oct. 23, 1951 E. o. HowLE ErAL APPARATUS FOR EXPANDINGPERLITE AND THE LIKE` 3 Sheets-Sheet 5 Filed Sept. 17, 1947 PatentedOct. 23, 1951 APPARATUS FOR EXPANDIN G PERLITE AND THE LIKE Ernest O.Howle and Roger W. Jackson, Chicago, Ill., and Norman M. Foster, NewCastle, Ind.; said Jackson and said Foster assignors to said HowleApplication september 17, 1947, serial No. 774,614

7 claims. (ci. 263-21) This invention relates to the expansion ofperlite, and among other objects, aims to provide a method of and meansfor more efliciently expanding perlite.

Another object of the invention is to increase the yield of expandedperlite.

Another object is to provide an improved method of and means forcontrolling the expansion of the perlite.

The nature of the invention and other objects and advantages thereofwill readily Pppear by reference to one illustrative method and appartusembodying the invention, described inthe following specification andillustrated in the accompanying drawings.

In said drawings:

Fig. 1 is an elevation, partly in section of the apparatus;

Fig. 2 is an elevation of adjustable driving means for feeding perliteto the expanding apparatus; and

Fig. 3 is a plan view of controlling means for the feeding apparatus;

Fig. 4 is an elevation of other details of such controlling means;

Fig. 5 is an elevation taken partly from the plane 5 5 of Figure 2, ofthe actuating means by which adhering perlite is dislodged from thewalls of the furnace;

Fig. 6 is a diagram of the thermostatic regulator for the feedingapparatus;

Fig. 7 (Sheet 2) is a sectional elevation taken from the plane 1 1 ofFig. 2, showing the delivery end of the feeding mechanism; and

Fig. 8 is a section taken on the plane 8-8 of Fig. 1, of a nozzle of theflame retention type.

'I'his application is a continuation in part of our copendingapplication Serial No. 684,452, later abandoned.

Perlite is a siliceous material of volcanic origin, and rhyolitic incomposition. It contains about 2 to 5% of combined water. When quicklyheated to its softening temperature range the steam formed puffs thematerial to many times its original size to produce a. material of verylow bulk density, e. g. 2 to 14 pounds per cubic foot, depending on thedegree and ei'ciency of expansion. Perlite differs considerably,depending on the locality where found, in the time required forexpansion, and in its softening range. The softening range is generallysomewhere between 1600 degrees F. to 2600 degrees F. A relatively widesoftening range is desirable to permit more eilicient and better controlof. expansion. It is difficult to prevent the material in its softenedcondition from cohering or agglomerating and from adhering to the wallsof the expanding furnace, with the result that much material is wastedand frequent removal of the layer of glass from the Walls of the furnaceis necessary. In this respect, among others, perlite presents seriousproblems not encountered in the treatment `of other materials. Even withthe most careful grading (which greatly increases the cost) it is notpossible to obtain material of sufficiently uniform grain size torespond alike to expanding temperatures. If the larger grains beexpanded properly, the smaller grains will be excessively softened,losing their porosity and adheringto other granules and to the walls ofthe furnace.

According to our invention, granules of various sizes may besimultaneously expanded without pregrading; and a given granule isexposed to expanding temperatures only long enough to expand it. Whenexpanded, and as a consequence of such expansion, it is automaticallyremoved from the expanding zone. The heavier or larger particles remainin the expanding zone a longer time. We utilize the large particle bulk(i. e. lower bulk density) resulting when the granule expands, to carrythe particle out of the expanding zone, by subjecting the granules to anupward current of gases of such velocity as to be capable of carryingthe particles away in the gas stream when adequately expanded. Until agranule expands, it remains in the highly heated expanding zone, itsbulk being insufficient to be levitated by force of the gas stream. Rockimpurities which do not expand, eventually fall below the heated zoneinto a collection space and are thereby automatically separated from theperlite.

This method of expansion may advantageously be used for expanding othermaterials such as vermiculite and mixtures of various expandablematerials. When expanded the bulk density of the material is low enoughto insure its being carried out of the expanding zone by the movinggases. Until adequately expanded it remains in the high temperaturezone. As regards mixtures, it is considerably cheaper to mix theexpandable materials in the proper proportion before expanding, thanafterwards; and the illustrative method and apparatus advantageouslypermits this because, regardless of size or character of the expandedmaterial, it remains in the high temperature zone until expandedsuiiiciently to be carried away with the upwardly traveling gases.

The broad subject matter involving expansion of the perlite byintroducing it into an upwardly rising stream of gases of such velocityas to carry the particles upward and out of the expanding heatimmediately on expansion of the particles Ibut not otherwise, is claimedin copending application Serial No. 39,048,

The serious problem of adhesion of the softened perlite to the furnacewalls is solved by employing a thin metal liner suspended inside thewalls of the furnace and separated therefrom so that it can be vibratedor otherwise slightly jarred or disturbed to dislodge any particlesthereon. Cooling air may be circulated outside the liner, and aspresently explained, excessive temperatures inside the liner areprevented by temperature responsive mechanism which adjusts the feed ofmaterials into the furnace to absorb excessive heat and to maintaintemperatures uniform inside the furnace.

In the illustrative furnace the liner comprises a cylindrical metal tubeor shell advantageously made of an alloy, such as stainless steel,capable of withstanding the temperatures to which it is exposed. In thisinstance its length is about twelve times its diameter. In theillustrative furnace its diameter is about l8 inches. It is indirect-lvsupported adjacent its upper end upon the refractory furnace wall fromwhich it is separated by a space I2 for the circulation of coolingfluid, in this case air.

The source of heat is a pre-mixed gas-red burner located at the lowerend of tube I0, comprising a gas nozzle I4 advantageously of the flameretention type (Fig. 8) and a tuyre Il whose mouth is located inside butseparated from the tube walls to provide a space I6 through which rockimpuritiemay escape from the furnace into a collecting box I1. The boxis sufficiently open to permit the passage of coolingr air therethroughto the coolingr space I2. 'I'he tuyre is advantangeously cooled by awater iacket I8 to which water circulatinc pines I9 and 20 areconnected. The flame retention nozzle I4 is characterized by a chamber2| surrounding the nozzle orifice 22 and supplied by gas from smallorifices 23. Gas velocitv in chamber 2| if relatively low (substantiallybelow that of the velocity of Fame propagation) and therefore serves tomaintain ignition of the high velocit` vas stream issuing from oriflce22, whch generally exceeds the speed of flame propagaton. The velocityof the gases issuing from the nozzle is, of course, high enough toinsure a velocity up the larger diameter expansion chamber sufficient tolevitate the material as and when it expands to a low bulk density.

A motor driven gas-air mixing, proportionlng and regulating unit 24supplies fuel and air to the burner. Its details are conventional andare not relevant to the present invention. In an expanding furnace likethat here illustrated having an internal diameter of 18 inches, we havefound that 2,000 cubic feet of natural gas per hour mixed 4with 18,800cubic feet of air will create a temperature during expanding operations,of about 1700 degrees F., on the outside of tube I about three feetabove the point where combustion starts. The temperature of the gases isof course substantially above this temperature (e. g. about 3000 degreesFJ, but the effective temperature, that is the temperature to which thegranules are heated is about 1700 to 1900 degrees F. The supply ofgranules normally present in the high temperature zone during operation,has a substantial cooling efl'ect on the hot gases. If the supply ofgranules be cut off or their rate of supply be subing zone would risesubstantially higher. Con' versely, in the presence of an increasedsupply of granules, the effective temperature would be lowered.

At their combustion temperature, the gases expand to such volume thatthe velocity of the gases up the tube is about 1100 feet per minute.This is sufficient to provide the force necessary to levitate perlitegranules having a maximum bulk density of about 8 pounds per cubic footand thereby carrying them out of the furnace when expanded. For heavieror larger granules the gas velocity is correspondingly increased (byincreasing the supply of gas and air) suiliciently to carry the granulesaway when they have been adequately expanded. Gas velocity may also beincreased by increasing the temperature, which correspondingly increasesthe volume of the gases, but this must be limited to proper expandingtemperatures.

The perlite may advantageously be fed into the furnace at a point justabove the point of maximum temperature of the flame, and as here shownthe perlite fed therein through an alloy spout 25 passing through anopening 26 in tube I0 large enough to permit the latter tube to expandand contract without disturbing the feeding spout 25. The latter iswidened at its outlet (see Fig. 7) to fan out the ore, and thereby todistribute it over the area of the furnace. Spout 25 is also equippedwith a baille 21 separate from the liner walls, but covering the opening26 in the liner.

As the perlite falls into the flame it is heated to expandingtemperatures and softened, and as soon as the material expandsadequately. its large bulk and low density causes the particle to becarried away with the rapidly upwardly traveling hot gases. Material notexpanded sufficiently remains in the expanding zone until it hasexpanded sufficiently. Unexpandable rock impurities eventually fallbelow the frame and escape through the space I6 between the lower end ofthe tube and the tuyre into the collection box The stack effect of theheated tube I0 induces a current of air to flow upwardly through spaceI2 to aid in cooling the tube. The tube is supported adjacent its upperend from a ring 3| surrounding the tube and welded or otherwise attachedthereto. The ring in turn is carried on a plurality of flexible orhinged suspension mem- Y bers 32 depending from a transverse open frame33 supported on the upper end of the refractory wall II by posts 34. Thetube thus hangs freely inside the furnace, and being unconnected at itslower end is free to expand and contract with changing temperatures.

Appropriate vibrating or jarring means are provided for periodicallyvibrating or jarring the tube so as to dislodge any particles of perlitewhich because of an excessively softened condition become attached tothe walls of the tube. Any appropriate mechanism of this character maybe employed. In the present case the vibrating mechanism is in the formof an anvil 38 connected with the tube support and a hammer 39 whichperiodically strikes the anvil to send a shock or vibration down thetube (see Figs. 2 and 5). The frequency of the hammer is in this casedetermined by the rate of rotation of the ore feeding screw. which isfrom 14 to 34 R. P. M.; but it is unnecessary that the frequency be thathigh or that it correspond to the rate of rotation of vthe feedingscrew. The hammer in this case is impelled by springs 4I connectedthereto and which are periodically compressed by the flexible connection42 extending to the ore feeding mechanism presently described (Figs. land 2) by which it is periodically pulled to compress the spring andthen periodically released. In the present case a cam 43 (slowly rotatedby the feeding screw) rocks lever 44 (pivoted at 45) to which theflexible line 42 is connected. Hammer 39 is thereby retracted, andsprings 4I compressed. The latter and lever 44 are suddenly releasedwhen the lever passes the high point 46 on the cam.

The material when expanded as above described is carried by the heatedgases out the top of tube I to a storage bin 41 to which it is connectedby the alloy elbow 48. The latter of course is highly heated by contactwith the hot granules and gases. Preferably it simply rests on the upperend of the tube supporting structure so that it may be readily removedfor inspection of the furnace and for replacement. The elbow is coveredby a jacket 49 spaced therefrom and hinged at its lower edge for accessto the elbow. A shield or baille 50 in the shape of an inverted troughdirects the hot granules down into the bin and protects the upperportion of the bin from direct heat from the granules. The lower portionof the bin being covered by granules is thereby insulated from the heatof the freshly expanded granules entering the bin.

In the illustrative bin a grading of the expanded perlite into threesizes is effected. The proportion of coarse, intermediate and lineexpanded material corresponds generally to the proportion of coarse,intermediate and fine material in the ore as fed into the furnace. Inthe present bin the aforesaid separation is effected by a baille whoseupper edge is so located in relation to the stream of material enteringthe bin, that the heavier and coarser material fails to clear the baillewhereas the finer material passes over it. As here shown, the baillecomprises the wall 53 which divides the bin into a compartment 54 forthe coarse material and a compartment 55 for the intermediate material.The upper edge E of the baille is ad'usted in relation to the stream ofmaterial entering the bin to effect the above separation. Bothintermediateand very fine material pass into compartment 55 where the nematerial which settles with difliculty is drawn Y into a cycloneseparator 51 through a tangential inlet 58. To prevent entrance into thecyclone separator of any intermediate grade material while suspended inthe stream, a baille 59 is placed across the path of the stream enteringcompartment 55 to remove the kinetic energy from the heavier particles,thereby causing these particles to fall to the bottom of compartment 55.Only the finer material which remains in suspension after striking thebaille enters the cyclone separator. The suction for the separator isprovided by fan El driven by motor 62. The ilne material is thrown outand falls to the bottom 63 of the separator from which it may beperiodically discharged into a collecting bin 64.

Weights of the various grades of expanded granules may be varied aspresently explained. When fully expanded the ne grade having a maximummesh size roughly of minus weighs 21/2 to 3 pounds per cubic foot. Theintermediate size having a maximum mesh size of minus 8 weighs about 4to 5 pounds per cubic foot; and the large size having a maximum meshsize roughthe hot particles in the bins from conduits 66v whosedischarge ends 6l are submerged in the mass oi' particles. The air isadvantageously supplied (by fans 68) by withdrawing it through pipes $9from the regions adjacent the tops of the bags 10 under the fillingspouts, to carry away the dust created on filling. The air dischargedinto the highly heated perlite also carries away some acid from theperlite (perlite is slightly acidic) thereby adapting it for uses whereperlite not so treated would be unsuitable. The subject matter involvingstoring and bagging is claimed in our copending application Serial No.793,926.

Encient operation of the furnace depends substantially on securingcomplete or efficient expansion of the granules without over-softeningthem to the point where they will collapse and cohere.

We have discovered that efficient and effective regulation of furnacetemperatures may be effected by varying the rate at which the perlite isintroduced into the furnace. Thus a much more prompt response of furnacetemperature is obtained than would be possible by attempting to regulatethe burner itself. It is thus possible to regulate the temperatureindependently of the Velocity of the gases of combustion, which have theadded function of carrying the material out of the high temperature zoneas and when it is properly expanded. Indeed, regulation by varying fuelsupply is impracticable because it correspondingly affects gas velocitywhose force is used to carry away the expanded granules. Reduction inthe supply of fuel for example would have the effect of reducing the gasvelocity and thus holding the ore in the furnace for a longer period,thereby neutralizing the control sought to be obtained by reduction intemperature through reduction in the supply of fuel.

On the other hand, we have discovered that the degree of expansion ofthe perlite, that is the Weight per cubic foot of expanded material, maybe varied by simultaneously varying the rate of i ore feed and the flowof fuel and air to the furnace. For example, a stronger material thanthat resulting from maximum expansion, may be desired, such as anaggregate for concrete. This, of course, weighs more per cubic foot thanthe material having maximum expansion. Contrary to what one mightexpect, reduction in degree of expansion (with increase in weight andstrength) may be effected by increasing the rate of fuel and ore feed.The increased rate of ore feed has a cooling eiect and prevents theundesired rise in temperature which would otherwise ensue. The increasedvolume of gas increases the velocity and levitating force of the gases,thereby carrying away the granules with a higher bulk density (i. e.expanded to a lesser degree) than would be the case if the gas velocitywere lower. The result is heavier and stronger granules.

Increase in degree of expansion (i. e. reduction in weight per cubicfoot of the material) may be accomplished in the reverse manner.

Variation in rate of fuel feed is of course 7 eected by regulation ofthe mixing and proportioning unit 24.

One illustrative ore feeding means is shown in Figs. 1 to 4. Anyappropriate feeding mechanism responsive to the furnace temperatures maybe employed. In the present case the perlite ore is supplied from a bin1| to a conveyor in the form of a screw conveyor 12. A valve 13 isadvantageously incorporated in the feed pipe 14 to interrupt feed ifdesired. The screw conveyor carries the ore to the feeding spout 25 downwhich it slides by gravity into the expanding zone of the furnace. Theconveyor is rotated at a speed varying roughly from 14 to 34 revolutionsper minute through a variable driving mechanism here shown in the formof an adjustable cone pulley drive. Such driving mechanism ischaracterized by driving and driven pairs of cone pulleys 15 and 16, thespacing of the former of which (15) may be varied to increase ordecrease the effective diameter'of the pulley and thereby to vary thedriving rate. The details of such driving mechanisms are well known andneed not be described beyond pointing out that in the illustrativedriving mechanism the cone sections of driving pulley 15 are drawntogether by springs which tend to increase the effective diameter of thepulley. By means of increasing the tension of the driving belt 11, thecones are wedged apart by the belt, thereby decreasing the speed ofrotation of the feed screw 12. Pulley 16 drives screw 12 through a speedreducer 18.

In the present regulating means, the belt driving motor 19 is slidablymounted on the base 80 to increase and decrease belt tension. It ismoved in this instance by a ratchet wheel 8| traveling on a stationaryscrew 82, carried by base 80. The rim of ratchet wheel 8| slidablyengages the motor base and, as the ratchet moves along the screw, itcarries the motor with it, either tightening or loosening the belttension. The ratchet wheel carries on its opposite faces oppositelydirected ratchet teeth 84 and 85 adapted to be selectively engaged by aforked pawl 86. The .pawl is oscillated by an eccentric' 81 (driven bymotor 19) through a connecting link 88 to which the pawl is pivoted(Figs. 2 and 4). The forks of the pawl comprise a pair of ratchetengaging members 89 and 90 adapted selectively to engage the ratchetteeth 84 and 85 onv the ratchet wheel. Y

Pawl 86 is made responsive to the temperature in the furnace, in thepresent instance, by athermostatic controlin the form of a thermocouple93 engaging the outside of the metal furnace shell (through an openingin refractory wall I I) and located so as to be responsive to the 'levelof temperature in the expansion zone of the furnace, that is the regionof maximum furnace temperature (Fig. 6). It is held in resilient contactwith the outside wall by springs 94, thereby maintaining contact duringmovement and vibration of tube I0. The thermo-couple is connected topyrometer 95 (see Fig. 6) which in turn (through conventional relaycircuits 96 and 91) controls solenoids 98 and 99. The latter rarealternately energized and serve to move predetermined value,thermo-couple 93 responds to increase the rate of feed of ore andthereby to reduce the temperature. Reduction in temperature in thefurnace below the predetermined level causes a reduction in the rate ofore feed, thereby permitting a rise in temperature. During neutralperiods when the pyrometer v95 is not energized, pawl 86 is held inneutral position and simply oscillates idly without operating ratchetwheel to vary the rate of feed. In such case the feed remains constant.

By means of the foregoing method and apparatus, it is possible to obtaina quality of material and an efficiency of operation not heretoforepossible. Imperfections in the exterior shell of the individual granulesare minimized, thereby greatly reducing water absorption and penetrationand increasing the strength of the granules in relation to their bulkdensity. Acidity of the granules is reduced by the method of circulatingair through the granules when highly heated.

Obviously the invention is not limited to the details of theillustrative method and apparatus, since these may be variouslymodified. Moreover, it is not indispensable that all features of theinvention be used conjointly since various features may be used toadvantage in different combinations and sub-combinations.

Having described our invention, we claim:

1. Apparatus for expanding mineral comprising in combination acylindrical sheet metal expanding chamber, a support for suspending saidchamber from a point adjacent its top so that it hangs freely from itssupport, a fuel supply introducing burning gaseous fuel into saidchamber to provide an expanding zone heated to temperatures suilicientto expand said minerals, a mineral feeder for introducing mineral to beexpanded into said high temperature zone, and mechanism for periodicallydelivering a blow to said metal walls to dislodge mineral materialadhering thereto.

2. Apparatus for expanding mineral comprising in combination anexpanding chamber having metal'walls, a fuel supply introducing burninggaseous fuel into said chamber to provide an expanding zone heated totemperatures sufficient to expand said mineralsl a mineral feeder forintroducing mineral to be expanded into said high temperature zone, anda thermostat in contact with said metal on the exterior of said chamberadjacent said high temperature zone, and mechanism responsive'to saidthermostat for regulating the effective temperature of said zone.

3. Apparatus for expanding mineral comprising in combination anexpanding chamber, a fuel supply introducing burning gaseous fuel into.said chamber to provide an expanding zone heated to temperaturessufficient to expand said minerals, a mineral feeder for introducingmineral to be expanded into said high temperature zone, a thermostat incontact with said metal wall on the exterior of said chamber adjacentsaid high temperature zone, mechanism for periodically agitating saidmetal walls to dislodge mineral adhering to said walls, mechanismresponsive to said thermostat for regulating the effective temperatureof said zone, and means for resiliently holding said thermostat againstsaid walls.

4. Apparatus for expanding mineral comprising in combination a verticalcylindrical metal tube open at its ends, means for suspendingthe tubeadjacent its upper end so that the same hangs freely, a burner at thelower end of said Q. tube for introducing burning fuel gas into thelower end of the tube to provide a high temperature expanding zone inthe lower portion of the tube, means for introducing mineral into saidhigh temperature zone, a thermostat in contact with the exterior of saidtube adjacent the'` high temperature zone for regulating the rate offeed of said mineral.

5. Apparatus for expanding mineral comprising in combination a verticalcylindrical metal tube open at its ends, means for suspending the tubeadjacent its upper end so that the same hangs freely, a burner at thelower end of said tube for introducing burning fuel gas into the lowerend of the tube to provide a high temperature expanding zone in thelower portion'of the tube, means for introducing mineral into said hightemperature zone, and mechanism for peri odically jarring said tube todislodge mineral adhering thereto.

6. Apparatus for expanding perlite comprising in combination a walledsupporting structure, an elongated tubular refractory metal shellin saidstructure and supported adjacent its upper end by said structure andhanging freely inside said structure and spaced from the walls thereof,the said space being constructed and arranged for passage of cooling airto cool Isaid shell, said shell forming an expansion chamber open at itsupper end, a burner adjacent the lower end of. said shell, means forprojecting from said burner an upwardly directed stream of'hot gasesthrough said shell of a velocity sumcient to levitate granules ofperlite when they have expanded substantially to reduce their bulkdensity, said velocity being insufficient to levitate unexpandablematerial, said chamber having an opening at its lower end to permitunexpandable material to fall downwardly out of said chamber, and` meansfor feeding granules of perlite into said stream oi'l hot gases.

7. Apparatus for expanding perlite comprising in combination anexpansion chamber comprising a substantially vertical elongated tubularshell vsupporting structure surrounding and spaced from the exterior ofsaid shell to provide acooling air space between the supportingstructure and the shell, means for supporting said tube at its ore intothe interior of said shell at a point above said burner.

. ERNEST O. HOWLE.

ROGER W. JACKSON. NORMAN M. FOSTER.

REFERENCES CITED The` following references are of record in the ille ofthis patent: l

UNITED STATES PATENTS Number Name Date 247,003 Beidler Sept. 13, 1881761,684 Kibler June 7, 1904 1,963,275 Iabus June 19, 1934 2,112,643Baensch et al. Mar. 29, 1938 2,129,523 Butler Sept. 6, 1938 2,203,821Hinchman June 11, 1940 2,210,103 Stoner Aug, 6, 1940 2,306,462 MoermanDec. 29, 1942 2,331,419 Patterson Oct. 12, 1943 2,334,578 Potters Nov.16, 1943 2,421,902 Neuschotz June 10, 1947 2,424,330 Robertson July 22,1947 2,431,884 Neuschotz Dec. 2, 1947 2,451,024 Ellerbeck Oct. 12, 1948OTHERREFERENCEB Perlite-Source of Synthetic Pumice IC 7364, Bureau ofMines, August 1946.

Kom: Thermal Studies of Obsidian, Pltchstone, and Perlite from Japan.Science Report Tohoku made of relatively thin gauge stainless steel and45 Imspelfial University Series 3 V01' 3' me 225" open at its upper and.lower ends, a refractory

1. APPARATUS FOR EXPANDING MINERAL COMPRISING IN COMBINATION ACYLINDRICAL SHEET METAL EXPANDING CHAMBER, A SUPPORT FOR SUSPENDING SAIDCHAMBER FROM A POINT ADJACENT ITS TOP SO THAT IT HANGS FREELY FROM ITSSUPPORT FOR SUSPENDING SAID DUCING BURNING GASEOUS FUEL INTO SAIDCHAMBER TO PROVIDE AN EXPANDING ZONE HEATED TO TEMPERATURES SUFFICIENTTO EXPAND SAID MINERALS, A MINERAL FEEDER FOR INTRODUCING MINERAL TO BEEXPANDED INTO SAID HIGH TEMPERATURE ZONE, AND MECHANISM FOR PERIODICALLYDELIVERING A BLOW TO SAID METAL WALLS TO DISLODGE MINERAL MATERIALADHERING THERETO.